Rex has already smelled the scent of Vampire lingering around the capital city, he reckoned that it was the Dark Elves that are visited by the royal representatives from the Vampire and the Werewolf Kingdom, not the Tigerman race.
It was odd but he came to a realization that King Samobas might still try to defy him.
As soon as he stepped into the throne room, the metallic odor of blood grew even more intense and overwhelming. It was oddly unguarded of the Vampire to be this careless about its presence, and let it be this detectable.
Knowing that he would come, the Vampire should be hiding its aura and scent not exposing them.
None of the Vampire aside from King Solomon can have a chance of actually defeating him, there are only a few entities of that caliber in the current era. In that case, the Vampire should be terrified of his presence alone.
But the Vampire did the exact opposite as if it wanted Rex to know of its presence.